<<XML has emerged as the lingua franca of service-oriented
infrastructures, forming the basis for all the SOA standards in vogue.
However, the performance gaps in SOA deployments due to verbosity and
voluminousness of XML, combined with chatty transport protocols is a
cause of concern. Different approaches have been suggested and adopted
to deal with this performance bottleneck, key among which are:
* XML compression including compact intermediate representations
* Caching
* Offloading via accelerators
* Transport-level optimization
* Optimized XML processing like specialized parsers for specific
schemas, etc.
While the first three approaches listed above are already mainstream
in commercial deployments in different products and custom
implementations, the latter two strategies of transport level
optimization and optimized XML processing are still to get the
attention of the SOA product community. We believe the experimental
results from these two approaches in the field are encouraging and
these approaches will become mainstream for tackling the SOA
performance challenge.
The notion of optimizing transport level protocols for better SOA
performance is important, given that SOAP, the fundamental SOA
protocol, rides on top of underlying transport protocols and is
transport agnostic. In these approaches, for end-to-end optimization
special attention is paid to optimize the transport protocol (e.g.
HTTP) to handle Web service payloads. To date, HTTP has emerged as the
prominent protocol to carry Web service payloads. In the recent past,
special attention has been paid to optimizing HTTP and HTTPS protocols
to get optimal performance for Web services.
For a detailed survey of existing transport level protocols used to
carry Web service payloads, see "Enhanced Transport Bindings for
Efficient SOAP messaging" published by the IEEE. Some related work out
of Cornell University also shows encouraging results for those
interested in optimization techniques.
Positive results have been demonstrated in these works by proving the
effectiveness of improving overall Web services performance by
leveraging optimized transport-level efficiency. While the Cornell
study shows good results via use of a reliable time critical multicast
protocol with probabilistic guarantees, the IEEE study shows an
innovative optimized application layer on top of UDP. Extending the
observations, some related approaches have leveraged HTTP compression
techniques to improve Web services performance. Likewise, TCP offload
techniques have shown to be highly effective in improving performance
of secure Web services requiring SSL.
Achieving the same objective of overall improvement of Web services
performance is yet another approach, namely that of optimized Web
service processing bypassing the usual complete life cycle of an XML
document parse/marshal/demarshal/re-parse. Some typical approaches
that have been suggested in this direction include Schema-specific
optimized parsers, usage of native payload format bypassing XML route,
etc. An optimistic set of results have been demonstrated in multiple
research works and experiments involving schema specific parsers (e.g.
WSDL specific parsers), including the work in "High Performance Web
Service specific SOAP processor" also published by the IEEE. Some
other approaches have shown the benefits in adopting more proprietary
and native payload formats (e.g. binary format as in CORBA/RMI) for
achieving better end-to-end performance.>>
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